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Low-redshift Lyman- α Blobs

Low-redshift Lyman- α Blobs. Mischa Schirmer Gemini Observatory, Chile. Collaborators: K. Ichikawa (NAOJ) T. Kawamuro (U Kyoto) S. Malhotra (Arizona State U) N. Levenson (Gemini South) H. Fu (U Iowa) R.E. Davies (MPE) C. Ricci (PUC)

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Low-redshift Lyman- α Blobs

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  1. Low-redshift Lyman-α Blobs Mischa Schirmer Gemini Observatory, Chile Collaborators: K. Ichikawa (NAOJ)T. Kawamuro (U Kyoto)S. Malhotra (Arizona State U)N. Levenson (Gemini South)H. Fu (U Iowa)R.E. Davies (MPE)C. Ricci (PUC) W. Keel (U Alabama)P. Torrey (CfA / MIT)J. Turner (Gemini South) Schirmer+ 2016, MNRAS, 463, 1554

  2. Outline: • LABs rapidly disappear with cosmic time • Ideal to study the Lyα escape mechanism • Why so few AGN in LABs

  3. LAB Fact Sheet: Luminous clouds of ionized gas Luminosities: Lyα ~ 1042 – 44 erg s–1 Size: 20 – 150 kpc Mostly at z = 2 – 3 Landmarks of massive galaxy formation Selecting Lyα using narrow-band imaging FAINT!! (hours of exposure time) Nilsson+ 2006 (z=3.16) Barger+ 2012 (z=0.97) Matsuda+ 2004 (z=3.1)

  4. Result #1: LABs still exist at low redshift! LABs are abundant in dense proto-clusters at z ~ 2. Keel+ (2009): GALEX search in cluster field at z ~ 0.8: Expected 30:Found 0 Prediction by Overzier+ 2013: LABs should still exist at low redshift: In the field (clusters too hot for cold accretion) Powered by AGN (cold accretion depletes) Rare Main result #1: YES, they do exist! Live in the field. Powered by AGN. Extremely rare.

  5. Low-z LABs (z ~ 0.3; r ~ 18 mag) Gemini GMOS gri-band images • [OIII], Lyα:1043 – 44 erg s–1 • Size: 20 – 80 kpc • GALEX FUV: Lyα bright! • Amongst most [OIII]-luminous objects known • 1 in 1000 deg2

  6. Project #1: How quickly do LABs go extinct? Density ~ (1+z)2...4 AGN model predictions ~1200 candidates from PanSTARRS (Dec 2016) + Gemini spec-z (poor weather program) + GALEX FUV / NUV cross-match

  7. Project #2: Studying the Lyα escape mechanism Resonant scattering

  8. Project #2: Studying the Lyα escape mechanism Lyα is key observable: – evolution of high-z galaxies – reionization of the Universe Lyα escape depends on: – Dust – Metallicity – Outflows – Neutral hydrogen Exploit high fluxes of 3 low-z LABs! Pilot study, resolving kpc scales, involving – Gemini: GMOS 3D spectra – Chandra + NuSTAR: soft+hard X-rays – HST: direct Lyα imaging and spectra

  9. Result #2: Why so few AGN in LABs? LABs → massive galaxy formation → growth of central black holes / AGN We don't see them in X-rays→ “They must be heavily obscured” “[...] requires particular combinations of geometric and radiative transfer effects to explain escape of Lyα while simultaneously maintaining obscuration along the line of sight.” (Steidel+ 2000) → Transient AGN Rapid duty cycles (104–5 years) (e.g. Schawinski+ 2015) AGN: 0.1 – 1% of time in quasar mode (Hopkins+2010; Novak+ 2011; Sijacki+ 2015) Francis+ 2001 (z=2.38)

  10. Result #2: Why so few AGN in LABs? – Transient AGN!

  11. Result #2: Why so few AGN in LABs? – Transient AGN!

  12. Result #2: Why so few AGN in LABs? – Transient AGN! Time of X-ray observation Main result #2: We do NOT expect to find luminous AGN in luminous LABs!

  13. Summary • We found low-z LABs • exist 4–7 billion years later in the Universe than other LABs • We explain ionization deficits with long-term AGN variability • We show that LABs rapidly disappear from the Universe • Very bright targets (r = 17...18 mag) to study AGN feedback, outflows, and Lyα escape fraction Schirmer+ 2016, MNRAS, 463, 1554

  14. Discussion slide: Time-dependent inflow rate – Many sharp bursts (“flickering”) c Quasar phases 1 million years Major merger Fig. credit: Hopkins & Quataert 2010, MNRAS, 407, 1529 (see also Novak+ 2011, DeGraf+ 2014, Sijacki+ 2015)

  15. Discussion slide: Broad-band selection of low-z LABs All brighter galaxies in CFHTLenS Low-z LABs are well separated in broad-band data due to powerful narrow-line emission. Why haven't you heard about them? Extremely rare: 3-4 Gpc3

  16. Discussion slide: Selection: searching in SDSS... Apply to SDSS data base: We overlooked: low-z LABs, the most luminous NLRs and outflows for 10 years! Bright, but rare: 4 Gpc–3 or 0.0011 deg–2 98% spurious detections!

  17. Discussion slide: Pre-discovery of J1155 – 0147 in 2001 Pre-discovery by QUEST ~2001; Chandra follow-up (PI: Coppi) in 2003, never published! OAN Venezuela; Photo credit: CIDA

  18. Discussion slide: IR response to a finite AGN pulse Time axis units: Light travel time to sublimation radius (t=1) Finite pulse, duration t=0.5 NIR (2.2 μm) Dusty torus models with increasing thickness MIR time lag: ~100-1000 years MIR (8.5 μm) Figure credit: Adapted from Hönig & Kishimoto 2011, A&A, 534, 121

  19. Discussion slide: More images of low-z LABs Bipolar Bipolar Multipolar Multipolar Bipolar Smooth Unipolar Train wreck Unipolar Train wreck Train wreck Unipolar / smooth

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